This is the U.S. National stage entry under 35 U.S.C. 371 of PCT/GB00/01914, filed May 18, 2000.
The present invention relates to edible compositions containing amorphous solid trehalose. The present invention also relates to methods of manufacture of compositions containing amorphous solid trehalose.
It is known to use sugar alcohols such as mannitol, sorbitol, xylitol, maltitol, isomalt, lactitol and erythirtol as non-cariogenic sweeteners in products such as boiled sweets, candy, chocolate and chewing gum. It is also known to use the sugar alcohols as excipients in the manufacture of medicaments for oral administration such as compressed tablets and lozenges to be sucked or chewed in the mouth. The drawback of such sweeteners is that they possess strongly endothermic heats of solution in the crystalline state, ranging typically from xe2x88x9239 kJ/kg for isomalt to xe2x88x92111 kJ/kg for sorbitol and xe2x88x92185 kJ/kg for crystalline erythritol (values are taken from the LFRA Ingredients Handbookxe2x80x94Sweeteners, J. M. Dalzell Ed., December 1996). Some sugars are also known to have strongly negative heats of solution. For example, dextrose monohydrate has a heat of solution of xe2x88x92105 kJ/kg.
Edible products or pharmaceuticals for oral administration containing ingredients with strongly negative heats of solution can give rise to a noticeable cooling in the mouth when the products are consumed. This cooling sensation is quite acceptable when the product contains menthol flavours such as mint, but it is undesirable when the product is non-menthol flavoured or the product is, for example, chocolate.
Trehalose is a naturally occurring non-reducing disaccharide. Specifically, trehalose is xcex1-D-glucopyranosyl-xcex1-D-glucopyranoside. It is present in certain drought-resistant plants such as Selaginella lepidophylia, and can also be prepared by fermentation. One suitable fermentation process is described in EP-A0693558.
GB-A-2206273 and GB-A-2187191 describe the use of trehalose as an additive to stabilize proteins and foodstuffs against degradation upon drying.
JP-A-60319503 describes the use of trehalose as a cryoproctectant for freeze-dried food. Up to 70% of trehalose on a dry weight basis is added to the food before freeze drying.
EP-A-0622025 describes the use of crystalline trehalose for the formulation of food products having reduced cariogenicity and calorie content compared to sucrose-containing sweeteners.
JP-A-92038642 describes confectionery compositions having low cariogenicity comprising trehalose and a sugar alcohol selected from erythritol, xylitol, mannitol, sorbitol, xylobiotol, maltitol and lactitol. These compositions apparently contain crystalline trehalose, probably trehalose dihydrate.
Crystalline trehalose dihydrate of the kind commercially available up until now has been measured by the present inventors to have a heat of solution of xe2x88x9252 kJ/kg. The present inventors have also found, surprisingly, that the heat of solution of amorphous trehalose formed by spray drying or melt spinning is actually positive, in the range 66-70 kJ/kg.
It is an object of the present invention to use the surprisingly exothermic heat of solution of amorphous trehalose to counteract the cooling effect in the mouth of food and pharmaceutical ingredients having endothermic heat of solution.
It is a further object of the present invention to use the surprisingly exothermic heat of solution of amorphous trehalose to provide novel processes for the production of foodstuffs and medicaments having a warming effect in the mouth.
Accordingly, the present invention provides an edible composition comprising at least 10% on a dry weight basis of one or more substances having an endothermic heat of solution of at least xe2x88x9230 kJ/kg and at least 10% on a dry weight basis of a substantially amorphous solid trehalose.
The term xe2x80x9csubstance having an endothermic heat of solutionxe2x80x9d refers to food- or pharmaceutically-acceptable substances that are soluble in water under physiological conditions and have an endothermic heat of solution of at least (i.e. at least as endothermic as) xe2x88x9230 kJ/kg
The substances having an endothermic heat of solution may for example be selected from the group consisting of soluble pharmaceuticals, pharmaceutically acceptable excipients, foodstuffs, flavorings, dietary supplements, or mixtures of such substances having negative heats of solution. Preferably, at least one of the substances having an endothermic heat of solution is a sweetener. For example, the substances may comprise dextrose monohydrate or even crystalline trehalose dihydrate. More preferably, the susbstances comprises a sugar alcohol. The term sugar alcohol refers to a hydrogenation product of a sugar. During hydrogenation, the aldehyde or ketone groups of the sugars are reduced to hydroxy groups. More preferably, the sugar alcohol is selected from the group consisting of mannitol, sorbitol, xylitol, maltitol, isomalt, lactitol, erythritol, and mixtures thereof.
Preferably, at least one of the substances having an endothermic heat of solution is substantially crystalline. Preferably, the substances having an endothermic heat of solution are soluble in water at 25xc2x0 C. to the extent of at least 25 g/liter, more preferably at least 100 g/liter. Preferably, at least one of the substances having an endothermic heat of solution is substantially anhydrous in the products according to the invention except for water of crystallisation, if any.
In any case, the one or more substances having an endothermic heat of solution exhibit a heat of solution equal to or more endothermic than xe2x88x9230 kJ/kg, more preferably more endothermic than xe2x88x9250 kJ/kg, and most preferably more endothermic than xe2x88x9270 kJ/kg.
Preferably, the edible composition according to the present invention comprises at least 20% by weight, of the substances having heats of solution equal to or more endothermic than xe2x88x9230 kJ/kg. Preferably, the edible composition according to the present invention comprises at least 20% by weight of amorphous trehalose. The edible compositions may, of course, comprise other edible or pharmaceutical components that do not contribute substantially to the heat of solution.
The solid trehalose is substantially amorphous. That is to say, it is characterized by a diffuse X-ray diffraction patter, as shown in FIG. 2. Amorphous trehalose can also be distinguished from crystalline trehalose by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), solid state nuclear magnetic resonance spectroscopy (NMR), microscopic techniques and other techniques.
Amorphous solid trehalose can be made by freeze-drying, spray drying, vacuum drying or over, drying aqueous solutions of trehalose. Amorphous trehalose can also be formed by melt spinning of solid trehalose in a candy floss-type machine. Preferably, the substantially amorphous solid trehalose has a heat of solution in water at 25xc2x0 C. of at least 30 kJ/kg, more preferably at least 60 kJ/kg. The latter value corresponds to substantially amorphous and anhydrous trehalose.
Preferably, the edible composition comprises less than 20% by weight of water, more preferably less than 10% by weight of water, and still more preferably less than 5% by weight of water. Higher water contents would cause the amorphous trehalose to revert to a crystalline form, or even to dissolve thereby making the heat of solution irrelevant to the sensation of the composition in a consumer""s mouth
Preferably, the weight ratio of the substance having an endothermic heat of solution to substantially amorphous solid trehalose is selected to modify the sensation of heating or cooling in the mouth when the edible composition is consumed. In practice, the weight ratio of substance having an endothermic heat of solution to trehalose is preferably in the range of 1:10 to 3:1, more preferably from 1:4 to 1:1. Preferably, the ratio of substance having an endothermic heat of solution to trehalose is selected such that the heat of solution of the edible composition is greater than (i.e. less endothermic than) xe2x88x9250 kJ/kg, more preferably greater than xe2x88x9230 kJ/kg, still more preferably greater than xe2x88x9215 kJ/kg, and most preferably greater than xe2x88x925 kJ/kg.
The present invention is especially suitable for edible compositions in which the substances having an endothermic heat of solution and the trehalose together make up a substantial fraction of the composition. Preferably, they together make up at least 25%, more preferably at least 50% and still more preferably at least 75%, at least 90% or at least 95% by weight of the composition.
More preferably, the composition consists essentially of sugar alcohols and/or sugars having an endothermic heat of solution and the amorphous trehalose, for example when the composition is a sweetener composition. More preferably, the sweetener composition is a free-flowing, particulate sweetener composition.
Other preferred edible compositions include chocolate, compressed tablets and hard sweets that are sucked in the mouth, and chewing gum. The edible compositions of this invention may form part of a larger foodstuff, for example the compositions may be present as a coating on an edible core. The edible compositions according to the present invention are also less calorific and less cariogenic than compositions having equivalent organoleptic properties made with conventional sugars such as sucrose.
In a further aspect, the present invention provides a method of manufacturing an edible composition comprising the step of dry mixing amorphous trehalose particles in an amount of at least 10% based on the dry weight of the composition with one or more other edible ingredients to form a dry mixture.
Preferably, the amorphous trehalose as hereinbefore defined is dry mixed in an amount of at least 20% by weight, more preferably at least 30% by weight based on the dry weight of the composition. The term xe2x80x9cdry mixingxe2x80x9d refers to mixing the particles substantially in the absence of water, preferably in the presence of less than 20% by weight of water, more preferably less than 10% by weight of water and most preferably less than 5% by weight of water. Preferably, the water content does not exceed these levels at any stage in the process after addition of the dry mixing step. This contrasts with the prior use of trehalose as a cryoprotectant in foodstuffs, where the trehalose is mixed with the aqueous foodstuff prior to freeze drying.
Preferably, the particle size of the trehalose used in the methods of this invention is less than 1 mm, preferably less than 0.1 mm, in order to achieve the desired intimate mixing.
The dry mixture preferably undergoes further processing steps, such as compressing the dry mixture to form a tablet, or forming the mixture Into a coating. In other preferred embodiments, the mixture further comprises a fat, and the method further comprises melting the fat In the dry mixture to form a fluid dry mixture, such as melted chocolate. Preferably, the dry mixture has substantially the same composition as the edible composition produced by the process.
The processes according to the present invention can be used to make compositions according to the present invention as hereinbefore described. The processes can also be used to make edible compositions containing little or no substances having endothermic heats of solution, in which case the edible compositions containing amorphous trehalose have a net exothermic heat of solution that gives the compositions a warming effect in the mouth when they are consumed. In these embodiments, the dry mixture in the process according to the present invention has an exothermic heat of solution in water at 25xc2x0 C. of at least +15 kJ/kg, more preferably at least +30 kJ/kg.
Preferably, the edible composition is selected from the group consisting of chocolate, compressed tablets, hard sweets that are sucked in the mouth, and chewing gum.